As of December 2020, the International Union for Conservation of Nature (IUCN) lists 52 data deficient avian species. 0.47% of all evaluated avian species are listed as data deficient. No subpopulations of birds have been evaluated by the IUCN. This is a complete list of data deficient avian species evaluated by the IUCN. Where possible common names for taxa are given while links point to the scientific name used by the IUCN.